Power transmissions, particularly multi-speed power transmissions of the automatic shifting type, utilize torque transmitting members or friction devices to transfer rotational movement and torque between transmission elements. One such torque transmitting member is the friction plate clutch, which enforces frictional engagement between interleaved disc elements formed in a friction pack, and alternately coupled with an input or output member. In some cases, the friction device is a brake and the output member is a stationary housing.
Torque transmitting mechanisms include a control mechanism, such as: fluid (hydraulic), mechanical, or electrical control mechanisms. Fluid-operated torque transmitting members have a piston disposed within a housing. The piston travels linearly in a cavity in the housing between an engaged position and a disengaged position, thereby causing selective engagement of the friction elements.